WASHINGTON--There's no doubt that YouTube is committing copyright infringement, so the central question is who must police its content, an attorney for Viacom said Friday.

After "months and months" of negotiations about that dilemma, failure to reach a resolution prompted Viacom "reluctantly" to file a $1 billion lawsuit against Google's video-sharing site earlier this week, said Don Verrilli, one of a team of Washington-based lawyers representing the media conglomerate.

Google and YouTube attorneys have argued that a provision of the 1998 Digital Millennium Copyright Act (DMCA) shields the company from infringement liability if it removes disputed clips promptly.

"We're confident and always have been that Congress intended with the DMCA to enable this type of service," Glenn Brown, product counsel for YouTube and Google, said in an interview earlier this week.

But that interpretation leaves Viacom with an unfair burden, argued Verrilli, who also argued Hollywood's U.S. Supreme Court case against file-swapping service Grokster and is a partner at the Jenner & Block law firm.

"What that means is we've got to employ an army of people around the clock who do nothing but monitor YouTube, catalog those works, (send takedown requests)...and find out the next day that the works go back up," he said at a panel discussion here hosted by the Progress and Freedom Foundation, a free-market think tank.

Verrilli said work has also grown increasingly handicapped by a YouTube feature that allows users to create private groups to share videos, which cannot readily be monitored by outsiders.

YouTube must know it is committing infringement because it already agrees to pull disputed videos when served with takedown notices, and it appears to have no problem filtering out videos whose content belongs to companies with whom it has already signed licensing deals, Verrilli said.

Furthermore it's hard to make a case that YouTube is an "innocent service provider" in the eyes of the law, he added. Under Section 512 of the DMCA, service providers may only benefit from the liability "safe harbor" if they meet a number of conditions, including not being aware of infringing activity and not making direct financial gain from it. In Viacom's view, Google does not meet those standards.

YouTube has done "a lot of social good that comes with a very significant problem," Verilli said. "And the significant problem that comes along with the good is that there is an enormous, enormous amount of copyrighted video works uploaded onto YouTube and viewed on a staggeringly high level by YouTube users."

Google has defended its practices throughout the week, going so far as to say YouTube's popularity has grown since the company recently agreed to remove clips at Viacom's request.

Existing partnerships with content owners like Warner Music Group, Sony BMG Music Entertainment, Universal Music, the BBC and the National Basketball Association "offer the YouTube community access to some of the best content in the world, ranging from entertainment and sports to politics and news," Google general counsel Kent Walker said in a statement the day the suit was announced. "And we're only getting started."

An executive speaking at a conference here on Thursday emphasized that Google believes it has strong legal backing under the DMCA and consequently hasn't started